Shotguns are a type of firearm that fire shells containing small pellets called shots, or solid projectiles called slugs. Shotguns are most commonly available in three configurations that are defined by how the weapon is loaded: a pump shotgun, a semi-automatic shotgun, and a break-action shotgun. A “pump” shotgun is loaded when the user cycles a sliding forearm to the rear and then forward again. This action ejects a fired shell casing from the chamber and loads a new shell from the magazine tube into the chamber. A “semi-automatic” shotgun cycles this ejection and loading process automatically for the user. A “break-action” shotgun has no magazine and is opened by the user who manually unloads and loads a single shell.
This disclosure relates to pump, semi-automatic, or any other shotgun configuration in which a magazine is employed. Such shotguns may generally include the following components: a barrel through which the shells are fired; a receiver through which the barrel is slidably or otherwise received; a chamber in which a shell is held prior to being fired from the barrel; a magazine tube in which shells are held in spring tension prior to introduction into the chamber; and a forearm that may be pulled to the rear of the shotgun to eject an old shell and load a new shell into the chamber (if the shotgun is a “pump” shotgun), as well as several other features. In practice, the barrel may be assembled onto the shotgun by sliding the back end of the barrel into the receiver and sliding a downwardly-extending ring of the barrel over the magazine tube. The barrel may then be locked in position with a cap that engages with an open end of the magazine tube and prevents the barrel from coming off of the weapon. In this way, the barrel of a shotgun may be exchanged so the shotgun can be used for different purposes.
Government regulations may dictate the shell loading capacity of a shotgun based on its intended application. Specifically, these regulations may specify the maximum number of rounds or shells that can be loaded into the magazine tube for each specific type of application of the shotgun. For example, for hunting upland game birds, the maximum allowable number of shells that can be loaded into the magazine tube of the shotgun may be three (two in the magazine tube and one in the chamber), while for home protection purposes the restriction to three rounds may be lifted, although such regulations may vary depending on the state. In order to avoid the need for different shotguns or magazine tubes with different shell loading capacities for various applications, shotgun users have sought strategies that permit the adjustment of the shell loading capacity of the magazine tube.
A common approach to control the shell loading capacity of a shotgun magazine tube is the use of a “plug” which is a device that occupies space in the magazine tube and limits the number of shells that can be loaded into the magazine tube. For example, U.S. Pat. No. 3,371,440 discloses a plug for removable insertion into a magazine tube to reduce the loading capacity of the magazine tube when hunting migratory birds. Although effective, a user must either disassemble the weapon to remove the plug and/or reassemble with a larger capacity magazine tube when using the shotgun for applications having lifted shell capacity regulations.
Another approach is to attach an add-on extension tube onto the open end of magazine tube to increase the shell loading capacity of the shotgun. Attachment of the extension tube onto a magazine tube of an existing shotgun may be accomplished by removing the cap from the open end of the magazine tube and connecting the open end of the extension tube to the open end of the magazine tube. However, since the cap on the open end of the magazine tube is used to secure the barrel to the shotgun, care should be taken to ensure that that the barrel is properly secured after the cap is removed and the extension tube is attached. This may be problematic with some current shotgun designs. Furthermore, in some shotgun designs, the extension tube may not rest tightly against the factory magazine tube and may not be in proper concentric alignment with the magazine tube. This may lead to a gap between the magazine tube and the extension tube in which the shells may become lodged and would thus cause a failure of the loading system.
Clearly, there is a need for more effective strategies for controlling the shell loading capacity of a shotgun for various applications.